Trig

the center of a circle
x^2 + y^2 + 8y =1 is
a. (0,-2)
b. (0,4)
c. (0,1)
d. (0,-4)
I believe the answer is (0,4)
Am I correct ?

  1. 👍
  2. 👎
  3. 👁
  1. Incorrect!

    you have to complete the square to get it into standard form

    x^2 + y^2 + 8y + 16 = 1 + 16
    x^2 + (y+4)^2 = 17

    Now what do you know from your previous posts on this?

    1. 👍
    2. 👎
  2. I'm not sure what your looking for Reiny. It looks like the center of the circle is still (0,4) what am I doing wrong?

    1. 👍
    2. 👎
  3. (x+0)^2 + (y+4)^2 = 17
    the center would be (0,4)
    I can't see it any other way ...arghhhh

    1. 👍
    2. 👎
  4. I pointed out the pattern for you in
    http://www.jiskha.com/display.cgi?id=1325732520
    and you seem to be able to understand in your posts that follow it,
    Now suddenly you have it backwards again.

    remember that the sign is opposite what you see in the brackets
    so for (x-5)^2 + (y+7)^2 = 100
    the centre would be (+5, -7)

    so for the above question is would obviously be
    (0, -4)

    1. 👍
    2. 👎
  5. ARGHHHHH now that really was a brain on my part ...
    Thanks a lot Reiny for the help
    Don

    1. 👍
    2. 👎

Respond to this Question

First Name

Your Response

Similar Questions

  1. Geometry

    Which one of these is NOT a step used when constructing an inscribed square using technology? A. Create a circle using the center with given points tool. B. Connect the points with a line through the center of the circle. C. Mark

  2. Geometry midpoint formula

    A circle on the Coordinate plane has a diameter with endpoints at (6,8) and (15,8). What are the coordinates of the center of the circle? What is the radius of the circle? Identify the coordinates of another point on the circle.

  3. Math - Answer Check

    Prove that circle A with center (–1, 1) and radius 1 is similar to circle B with center (–3, 2) and radius 2. From A to B: (x - 2, y + 1), scale factor 2?

  4. Geometry

    The question is to find the measure of arc PQ in Circle A. The point A is the center of the circle, and the chords PR and SQ intersect at the center. Arc PQ is (3y-10), while arc SR is (2y+20). I know there's a theorem that states

  1. math

    In the x y − xy− plane, the center of a circle has coordinates ( 6 , 10 ) (6,10) and the circle touches the y − y− axis at one point only. What is the radius of the circle

  2. GEOMETRY INSCRIBED ANGLES MULTIPLE CHOICE QUESTION

    segment BC is tangent to circle A at B and to circle D at C. (Not drawn to scale) AB=10 BC=25 and DC=3. Find AD to the nearest tenth. Hint: Draw an auxiliary line from D to segment BA. {There are two circles, the larger one has

  3. gEoMeTrY iNsCrIbEd AnGlEs MuLtIpLe ChOiCe QuEsTiOn

    A satellite, B, is 17,000 miles from the horizon of Earth. Earth’s radius is about 4,000 miles. Find the approximate distance the satellite is from the Earth’s surface. {The picture is a circle with point O in the center,

  4. GEOMETRY

    The diameter of a circle has endpoints P(–10, –2) and Q(4, 6). a.Find the center of the circle. b.Find the radius. If your answer is not an integer, express it in radical form. c.Write an equation for the circle.

  1. Physics

    The large blade of a helicopter is rotating in a horizontal circle. The length of the blade is 6.7m, measured from its tip to the center of the circle. Find the ratio of the centripetal acceleration at the end of the blade to that

  2. math

    4x^2+4y^2-16x-24y+51=0 is the equation of a circle. where is the center of the circle and what is it's radius? A. center (2,3) radius=1/4 B. center (2,3) radius=1/2 C. center (-2,-3) radius=1/4 D. center (-2,-3) radius=1/2

  3. Math

    Rosario noticed that the distance from the pole in the center of the tetherball circle to the painted circle was about six feet.What was the approximate radius of the tetherball circle?

  4. NEED MAJOR HELP! *QUADRATIC EQUATIONS*

    Write the equation for the circle with center at (- 8, - 6) and radius of 10. (x+8)² + (y + 6)² = 10 (x+8)² + (y + 6)² = 100 (x-8)² + (y - 6)² = 100 Find the standard equation for the circle with center on the positive

You can view more similar questions or ask a new question.